[PATCH 3/3] PCI: hv: delete the device earlier from hbus->children for hot-remove

[KY Srinivasan]

> -----Original Message-----
> From: Dexuan Cui
> Sent: Wednesday, November 9, 2016 11:20 PM
> To: Bjorn Helgaas <bhelgaas at google.com>; linux-pci at vger.kernel.org;
> devel at linuxdriverproject.org
> Cc: gregkh at linuxfoundation.org; KY Srinivasan <kys at microsoft.com>;
> Haiyang Zhang <haiyangz at microsoft.com>; Stephen Hemminger
> <sthemmin at microsoft.com>; Jake Oshins <jakeo at microsoft.com>; Hadden
> Hoppert <haddenh at microsoft.com>; Vitaly Kuznetsov
> <vkuznets at redhat.com>; jasowang at redhat.com; apw at canonical.com;
> olaf at aepfle.de; linux-kernel at vger.kernel.org
> Subject: [PATCH 3/3] PCI: hv: delete the device earlier from hbus->children
> for hot-remove
> 
> After we send a PCI_EJECTION_COMPLETE message to the host, the host will
> immediately send us a PCI_BUS_RELATIONS message with
> relations->device_count == 0, so pci_devices_present_work(), running on
> another thread, can find the being-ejected device, mark
> the hpdev->reported_missing to true, and run list_move_tail()/list_del()
> for the device -- this races hv_eject_device_work() -> list_del().
> 
> The patch moves the list_del() in hv_eject_device_work() to an earlier
> place, i.e. before we send PCI_EJECTION_COMPLETE, so later the
> pci_devices_present_work() can't see the device.
> 
> Signed-off-by: Dexuan Cui <decui at microsoft.com>
> CC: Jake Oshins <jakeo at microsoft.com>
> Cc: KY Srinivasan <kys at microsoft.com>
> CC: Haiyang Zhang <haiyangz at microsoft.com>
> CC: Vitaly Kuznetsov <vkuznets at redhat.com>

Thanks Dexuan.

Acked-by: K. Y. Srinivasan <kys at microsoft.com>
> ---
>  drivers/pci/host/pci-hyperv.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 7590ad0..fe5179d 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -1582,6 +1582,10 @@ static void hv_eject_device_work(struct
> work_struct *work)
>  		pci_dev_put(pdev);
>  	}
> 
> +	spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
> +	list_del(&hpdev->list_entry);
> +	spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
> +
>  	memset(&ctxt, 0, sizeof(ctxt));
>  	ejct_pkt = (struct pci_eject_response *)&ctxt.pkt.message;
>  	ejct_pkt->message_type.type = PCI_EJECTION_COMPLETE;
> @@ -1590,10 +1594,6 @@ static void hv_eject_device_work(struct
> work_struct *work)
>  			 sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
>  			 VM_PKT_DATA_INBAND, 0);
> 
> -	spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
> -	list_del(&hpdev->list_entry);
> -	spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
> -
>  	put_pcichild(hpdev, hv_pcidev_ref_childlist);
>  	put_pcichild(hpdev, hv_pcidev_ref_pnp);
>  	put_hvpcibus(hpdev->hbus);
> --
> 2.7.4